The present invention relates generally to photooxidation products, and derivatives thereof, of Merocyanine 540, their preparation and their therapeutic uses.
Photodynamic therapy (PDT) is an ancient concept. PDT usually involves the administration of one or more photoactive agents, or dyes, to the subject to be treated followed by exposing the specific target location or target organ of the subject to light.
The emphasis on using a photoactive compound or dye as the photoactivating or light-activating compound in photoradiation or tumors or viruses is based on two important properties of the photoactive compound or dye. Firstly, the photoactive compound or dye is preferentially accumulated and retained to a higher degree in or around the target tumor or virus than in the surrounding normal body tissues. Secondly, after being retained in or around the tumor or virus, the photoactive compound or dye is properly photoactivated causing the destruction of tumor cells or virus with which the dye has associated. The destruction of tumor cells or virus occurs when they are simultaneously exposed to the dye and light of a suitable wavelength. The generally accepted mechanism of cell kill by photoactivated dye is that when activated by appropriate light, the dye undergoes an energy transfer process with oxygen to form a reactive but extremely short-lived singlet oxygen, which subsequently oxidizes and kills the cell or inactivates virus to which the dye has attached or associated as a substrate. K. R. Weishaupt, C. J. Gomer, and T. J. Dougherty, Cancer Res. 36: 2326-29 (1976); F. Sieber, Photochem. and Photobiol. 46: 1035-42 (1987).
U.S. Pat. No. 4,649,151 teaches the preparation and purification of porphyrin-type drugs. The patent also teaches the diagnosis and destruction of cancer cells with porphyrin-type drugs. In treating humans or other mammals with the drugs, light must be irradiated on the cancer cells in such a position as to uniformly illuminate the cancer cells. When cancer cells, having the porphyrin-type drugs associated therewith, are illuminated with light, the drugs are activated and thus causing the destruction of the cancer cells by a mechanism not completely understood yet. The patent also discloses several apparatus for transmitting light to different parts of the body.
U.S. Pat. No. 4,614,190 discloses that while a dye such as hematoporphyrin derivative ("Hpd") is being held within the tumor cells in the body, the activation of the dye is accomplished by pulsed electromagnetic radiation.
U.S. Pat. No. 4,727,027 teaches the inactivation of pathogenic biological microorganisms by simultaneous treatment with furocoumarins and a long wavelength ultraviolet light under conditions which limit the availability of oxygen and other reactive species.
U.S. Pat. No. 4,684,521 teaches a chemical agent for the reduction of the population of a selected blood constituent having receptor sites. The invention uses a photoactive agent physically incorporate within or chemically bound to a carrier molecule. The carrier molecule has a strong affinity for the receptor sites on the blood constituent. When activated by Ultraviolet ("UV") radiation, the photoactive agent bound to the carrier molecule interferes with the metabolism of the selected blood constituent.
U.S. Pat. No. 4,612,322 discloses a method and system for externally treating human blood to reduce the functioning lymphocyte population in the blood system. According to the method, blood is treated with a photoactive agent and simultaneously irradiated with UV radiation outside the body.
U.S. Pat. No. 4,708,715 teaches a removable UV light array assembly for use in a patient system wherein photoactivatable agents, in contact with patient blood cells, are irradiated extracorporeally and then returned to the patient.
Cyanine dyes are members of another class of dyes that are selectively retained by tumor cells and certain viruses. For example, Merocyanine 540, (commonly referred to as MC 540) has been used for light-induced tumor and viral chemotherapy. K. S. Gulliya, J. W. Fay, R. M. Dowben, S. Berkholder and J. L. Matthews, Cancer Chemotherapy Pharmacol. 22: 211-14 (1988); K. S. Gulliya, S. Pervaiz, Blood 73: 1059-65 (1989); F. Sieber, Photochem. and Photobiol. 46:1035-42 (1987).
The currently accepted method of practicing PDT is to first let the photoactive compound bind, or get close, to the target tumor cells or viruses, and then activate the photoactive compound by a high fluence rates of light. Thus, when the reactive singlet oxygen is generated from photoactivation, the target tumor cells or viruses that are in the close proximity to the activated dye and oxygen are destroyed. The normal cells do not preferentially accumulate the photoactive compound, hence generally very little reactive singlet oxygen is generated in their close proximity. Accordingly, the normal cells are generally spared from destruction by the photoactivated photoactive compound. T. J. Dougherty, et al., Photoradiation Therapy: Clinical and Drug Advances. In Prophyrin Photosensitization, D. Kessel and T. J. Dougherty, Eds. Plenum Press, N.Y., pp. 3-13, 1983.
PDT, however, has one major limitation in practical utility, that is, in order to eradicate from the animal body the tumor cells or viruses on which the photoactive compound or dye neighbors or resides, such cells or viruses must be exposed to an appropriate light source. PDT is efficient only in cases where the entire tumor can be reached by light. Hence tumors thicker than 5-7 mm are rarely eradicated by PDT. Thus, to achieve the desired killing, one must find, if at all possible, the target tumor cells or viruses which have preferentially accumulated the photoactive compound, and then one must irradiate these target cells inside the animal body with a light source directly. If the tumor, such as solid tumor, is large enough and localized that it can be seen by naked eyes, then the dye can be injected into the tumor itself. Even after this, however, there is still the problem of introducing light into the inner portions of the tumor. Moreover, during metastasis, the tumor cells or viruses have spread to other parts of the body and are no longer localized. The dilemma after the introduction of photoactive compound to the patient is: Where should the irradiation be given? Even assuming that the malignant tumor cells can be localized and found in one particular body tissue or organ, many body tissues and internal organs where tumor cells or viruses have proliferated are nonetheless inaccessible to any light.
Another major limitation to PDT is that the light energy itself, in particular the ultraviolet light, is toxic and can be mutagenic to normal cells as well normal tissues. Thus, many photoactive compounds that can be activated best by ultraviolet light cannot be used in the clinic because the ultraviolet light required for the activation of the photoactive compounds would be exceedingly harmful to the surrounding normal tissues and the normal cells.
Further, patients undergoing the traditionally PDT treatment must remain in the dark for a long period of time until the photoactive agents used have cleared out of the patient's system.
To overcome many of the disadvantages of PDT, U.S. Pat. No. 5,091,385 to Gulliya, et al. discloses a pre-activated therapeutic agent derived from a photoactive compound for destroying tumor or other pathogenic biological contaminants infecting an animal body tissue. The disclosure of this U.S. patent is herein incorporate in its entirety by reference. This reference discloses that the activation of the photoactive compound is carried out prior to the photoactive compound is being brought into contact with the tissue to be treated. The resultant pre-activated therapeutic agent, or mixture or agents, retains its therapeutic activity subsequent to activation.
The method of preparing pre-activated therapeutic agent disclosed in the U.S. Pat. No. 5,091,385 often produces a mixtures of products or ingredients. Although some of the products produced by this pre-activation show biological activities, most likely, some of the products are biologically inactive.
Thus, there is a need to isolate, purify and identify the active products derived from the pre-activation of a photoactive compound. A purified active product is essential for its therapeutic uses.